1. Field of the Invention
The present invention relates to the field of video mixers, also known as video switcher or video edit gear, and particularly to the field of automated video communication and control between a video mixer and a computer.
2. Art Background
With the advent of video technology in image recording, it has become more and more common to use a video mixer for editing video tapes. Video tapes offer many attractive features. In video recording there are no foot cuts and no rolls of film to unravel and no footage is lost. A first cut in video, or any other screening, can be easily saved and reshown at any time. Complicated video effects can also be accomplished off-line that would look as real and immediate as they were done on-line. Finally, aside from any delay due to editorial decisions, videotape editing is undoubtedly much faster than film editing.
An illustrative example of such a videotape editing system can be found in the Edit Gear, XV-Z10000, manufactured by the Sony Corporation of Tokyo, Japan. With a touch of buttons on the control panel, or "switcher head," video signals can be combined, mixed, switched, overlapped, inserted, duplicated, miniaturized, interwoven, compressed, zoomed, scrolled, and etc., to create a variety of special effects. FIG. 1a illustrates some of the functions of the XV-Z10000.
As demonstrated in FIG. 1b, the XV-Z10000 consists of two physical units: a main chassis 300 and a switcher head 110. The main chassis 300 is the control unit, where input 120 and output 130 video signals are connected to be processed. The main chassis 300 utilizes a 4-bit microcomputer 101 for processing. The switcher head 110 is the "button panel" which selects the desired effects such as wipe pattern, luminance, chrominance, and zoom effect.
Reference is now made to FIG. 2, where the timing scheme for the XV-Z10000 communication protocol is shown. The communication protocol between the main chassis 300 and the switcher head 110 is known as the "3-point serial," comprising a BEGIN signal which indicates a frame, an INTERVAL (INT) signal which indicates a byte, and a clock (SCLK) which represents a bit. As is shown in FIG. 2, there are currently 8 (bits) cycles of SCLK for each INT (byte) and 32 INT's for each BEGIN (frame).
It can be appreciated that operating the XV-Z10000 edit gear still requires manual operation of key buttons, which imposes a limitation as to how many buttons, or functions, a human operator's hands can manipulate in each frame. It can also be appreciated that the human operator is required to be at the "box" to operate because the XV-Z10000 is a stand-alone unit without any remote accessibility. Further, it can be appreciated that where an edit decision in one frame is identical to a previous frame, a human operator still has to re-key in the buttons. Worse yet, to perform an identical sequence of editing, as may occur if the editing is to be performed in a different location or at a different time, a human operator has to re-do the entire sequence with the utmost tedium. Finally, it can be appreciated that a human video editor still has to be physically at the "box" to make editing decisions, although it would be more efficient to be able to make edit decisions at a remote site. In a typical editing studio with multiple rooms and multiple edit gears, an editor will go from room to room to perform edits, although a centralized control environment would be more efficient.